Question: Worked Examples
1 Graph $y \geq x^2 - 2$
2 Graph $y < x^2 + 2x - 3$
3 Graph $x^2 + y \leq 16$
4 Graph $y > -x^2 + 6$
5 Graph $y \leq x^2 - 4x + 1$
Solve for the x-intercept, vertex, test point and graph
1. **Problem Statement:** Graph the inequality $y \geq x^2 - 2$ and find the x-intercept, vertex, and test point.
2. **Formula and Rules:** The graph is a parabola of the form $y = ax^2 + bx + c$ with $a=1$, $b=0$, $c=-2$. The vertex formula is $\left(-\frac{b}{2a}, c - \frac{b^2}{4a}\right)$.
3. **Find the vertex:**
$$x_v = -\frac{0}{2 \times 1} = 0$$
$$y_v = -2$$
Vertex is at $(0, -2)$.
4. **Find the x-intercepts:** Set $y=0$:
$$0 = x^2 - 2$$
$$x^2 = 2$$
$$x = \pm \sqrt{2}$$
5. **Test point:** Choose $x=0$, then $y = 0^2 - 2 = -2$. Since $y \geq x^2 - 2$, test point $(0,0)$:
$$0 \geq 0^2 - 2 \Rightarrow 0 \geq -2$$
True, so shade above the parabola.
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1. **Problem Statement:** Graph $y < x^2 + 2x - 3$ and find x-intercept, vertex, test point.
2. **Vertex:**
$$a=1, b=2, c=-3$$
$$x_v = -\frac{2}{2 \times 1} = -1$$
$$y_v = (-1)^2 + 2(-1) - 3 = 1 - 2 - 3 = -4$$
Vertex at $(-1, -4)$.
3. **X-intercepts:** Set $y=0$:
$$0 = x^2 + 2x - 3$$
$$x^2 + 2x - 3 = 0$$
$$(x+3)(x-1) = 0$$
$$x = -3, 1$$
4. **Test point:** Use $(0,0)$:
$$0 < 0^2 + 2(0) - 3 = -3$$
$$0 < -3$$
False, so shade below the parabola.
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1. **Problem Statement:** Graph $x^2 + y \leq 16$.
2. **Rewrite:**
$$y \leq 16 - x^2$$
3. **Vertex:**
$$a = -1, b=0, c=16$$
$$x_v = 0$$
$$y_v = 16$$
Vertex at $(0,16)$.
4. **X-intercepts:** Set $y=0$:
$$0 = 16 - x^2$$
$$x^2 = 16$$
$$x = \pm 4$$
5. **Test point:** $(0,0)$:
$$0 \leq 16 - 0 = 16$$
True, shade below the parabola.
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1. **Problem Statement:** Graph $y > -x^2 + 6$.
2. **Vertex:**
$$a = -1, b=0, c=6$$
$$x_v = 0$$
$$y_v = 6$$
Vertex at $(0,6)$.
3. **X-intercepts:** Set $y=0$:
$$0 = -x^2 + 6$$
$$x^2 = 6$$
$$x = \pm \sqrt{6}$$
4. **Test point:** $(0,0)$:
$$0 > -0 + 6 = 6$$
False, so shade above the parabola.
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1. **Problem Statement:** Graph $y \leq x^2 - 4x + 1$.
2. **Vertex:**
$$a=1, b=-4, c=1$$
$$x_v = -\frac{-4}{2 \times 1} = 2$$
$$y_v = 2^2 - 4(2) + 1 = 4 - 8 + 1 = -3$$
Vertex at $(2, -3)$.
3. **X-intercepts:** Set $y=0$:
$$0 = x^2 - 4x + 1$$
Use quadratic formula:
$$x = \frac{4 \pm \sqrt{(-4)^2 - 4(1)(1)}}{2} = \frac{4 \pm \sqrt{16 - 4}}{2} = \frac{4 \pm \sqrt{12}}{2} = \frac{4 \pm 2\sqrt{3}}{2} = 2 \pm \sqrt{3}$$
4. **Test point:** $(0,0)$:
$$0 \leq 0^2 - 4(0) + 1 = 1$$
True, shade below the parabola.
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**Final answers:**
- Each parabola's vertex and x-intercepts are found.
- Test points confirm shading region.
- Graphs are parabolas opening up or down with shading as per inequality.